Predatory selection of mucoid, antibiotic resistant Pseudomonas putida phenotype by myxobacterium Cystobacter ferrugineus

Abstract

Predation contributes to the structure and diversity of microbial communities. Predatory myxobacteria are ubiquitous to a variety of microbial habitats and capably consume a broad diversity of microbial prey. Predator-prey experiments utilizing myxobacteria have provided details into predatory mechanisms and features that facilitate consumption of prey. However, prey resistance to myxobacterial predation remains underexplored, and prey resistances have been observed exclusively from predator-prey experiments that included the model myxobacterium Myxococcus xanthus. Utilizing a predator-prey pairing that instead included the myxobacterium, Cystobacter ferrugineus, with Pseudomonas putida as prey, we infrequently observed surviving phenotypes capable of eluding predation. Comparative transcriptomics between P. putida unexposed to C. ferrugineus and the survivor phenotype suggested that increased expression of efflux pumps, genes associated with mucoid conversion, and various membrane features contribute to predator avoidance. The P. putida survivor phenotype was confirmed to be resistant to the antibiotics kanamycin, gentamicin, and tetracycline and to produce more alginate, pyoveridine, and phenazine-1-carboxylic acid than predator-unexposed P. putida. Unique features observed from the survivor phenotype including small colony variation, efflux-mediated antibiotic resistance, phenazine-1-carboxylic acid production, and increased mucoid conversion overlap with traits associated with Pseudomonas aeruginosa predator avoidance and pathogenicity. The survivor phenotype also benefited from increased predator resistance during subsequent predation assays. These results demonstrate the utility of myxobacterial predator-prey models and provide insight into prey resistances in response to predatory stress might contribute to the phenotypic diversity and structure of bacterial communities.